The Confessions singer underwent rigorous boxing training to play the retired champion in the upcoming film Hands Of Stone.

"What he did as a boxer is no different from what I do as a dancer. I train like an athlete every day, believe it or not," the 34-year-old told the November issue of US Men's Health.

Usher, whose full name is Usher Raymond IV, has gone to great lengths to get into character and and even met with Sugar Ray himself.

"My commitment to this character demands that I not only physically get ready, but also become him. The hair, the personality, the manner he conducts himself in, all that. He's an incredible man," he said.

He has taken tips from another ring champion.

"Sugar Ray Robinson said the most potent weapon in boxing is rest. Now I realise you can't push yourself all the way. You have to pull back a little bit," he explained.

"Mentally, I'm the type of person who can ignore the pain. Put it somewhere else and allow my body to just go there. But I always suffer. You can't box, ride a bike for 20 miles in the heat - Georgia heat - and then go to the studio and rehearse. That's not happening."

Usher also revealed how he moved to New York to work with Sean 'P Diddy' Combs when he was 14. The pair spent long hours in the recording studio, before partying in clubs.

"My childhood wasn't like the average kid's. That's not really great for a young boy. But I didn't know," he added.